1. Field of the invention
Present invention relates to structural proteins like collagen repairs in general, while, more specifically it relates to a method of photochemical cross linking of collagen fibrils using photoactive agent, whereby it could be used in different types of tissue repair and regeneration in human and animals.
2. Invention Disclosure Statement
The protein: collagen is the main substance of connective tissue and is present in humans. In mammals collagen is the most abundant protein. Collagen gives many different organs and tissues support and elastic properties. It has been found in many different tissues and organs like bones, tendons, (hyaline) cartilage, blood vessels, teeth, cornea, skin, etc. It prevents organs/tissues to tear or loose their functional shape when they are exposed to sudden and wild movements.
Collagens are fibrous protein composed on amino acids. The most abundant amino acids are glycine, proline and hydroxyproline. General collagen structure consists of three polypeptides, each of which is a left-handed helix, intertwined into a right-handed triple helix. Human body is mainly composed of collagen type I.II.III, however many other types are also present.
Collagen is a natural biomaterial commonly used in tissue engineering and repair; it has negligible immune rejection and excellent biocompatibility. But unprocessed collagen is mechanically weak and vulnerable to chemical and enzymatic attacks that limits its use.
Collagen can be cross-linked to increase its molecular stability and mechanical properties. The most basic mode of action is the covalent intermolecular cross-link formation between collagen fibrils. Cross-linking improves strengths, resorption rate and biocompatiblilty of the scaffold.
The collagen can be strengthen and stabilized, either by chemical or physical methods of cross-linking. In Chemical method, some chemical cross-linking agents include: glutaraldehyde, formaldehyde, 1-ethyl-3(3-dimethylaminoproplyl)-carbodimide (EDC) etc are used for cross-linking to improve the Physico-chemical properties of collagen; however, this method is limited because of induction of cytotoxicity and calcification and stiffness in host tissue due to incomplete removal of the toxic residues, aldehydes, and other metabolites. Physical methods of cross-linking can be achieved by heat, dehydrothermal treatment (DHT), and UV- and γ-irradiation. These methods compromise the stability of collagen due to thermal degradation and collagen denaturation is bound to occur due to heat. These cross-linking processes are very time comsuming, usually requiring hours or days to completer and cause significant degradation to the collagen molecules.
Photochemical method provides and alternative method for cross-linking collagen in the presence of light and photosensitizing agents. In U.S. Pat. 6,783,539 by Timberlake et al., discloses uses of phototriggerable tethered diazopyruvate composition and method for crossing linking of proteins using the same. A wavelength range of 330-400 nm is used for activation of photoactive compound and cross-linking of the protein. The wavelength range used here minimal penetration and is useful only for certain medical application. Cross-linking is done prior to application in vivo.
A better method of collagen cross linking needs to be developed which would in turn improve the physio-chemical properties of collagen such as water-binding capacity, mechanical properties and thermostability thus enhancing better tissue healing without scaring or damaging the collagen. The present invention aims to provide this.
Objectives And Brief Summary Of The Invention
It is an objective of the present invention to provide a photochemical method for cross-linking of collagen in vivo.
It is another objective of the present invention to provide a non-toxic photoactive formulation with collagen.
It is still another objective of the present invention to use such photochemical cross linking method for tissue engineering and repair.
It is also another objective of the present invention to use a suitable wavelength matching the absorption spectrum of photoactive compound.
It is further objective of the present invention to use the photochemical cross-linked collagen in wound closures and cosmetic applications.
It is yet another objective of the present invention to provide a non-toxic, highly stable collagen scaffold, having optimal pore size.
Briefly stated present invention provides a method and compositions for photochemical cross linking of collagen by photoactive agent in-vivo. The method includes a non-toxic photoactive formulation of the composition with collagen, which is administered to treatment area locally followed by irradiation with suitable wavelength. In one of the embodiment liposomal formulated mTHPC is added to the collagen and is irradiated with a 652 nm laser, resulting in producing efficient collagen scaffolds with strengthened and stabilized microstructure, thus improving the physiochemical properties of the collagen scaffold. It improves the thermostability, mechanical property and swelling ratio of newly formed scaffold. Photochemical cross-linking of collagen in vivo also shows an antimicrobial effect. When irradiated with a suitable wavelength, it disinfects the treatment site and curbs microbial growth.
The above and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings.